Filter unit



Nov., 11, 1952 M. H. HAWLTON 2,517,535

FILTER UNIT Filed NOV. 5, 1948 f 'TH-l- Patented Nov. 1l, 1952 UNITEDSTATES PATENT OFFICE FILTER UNIT Miles H. Hamilton, Los Angeles, Calif.,assignor to United Aircraft Products, Inc., Dayton, Ohio, a corporationof Ohio Application November 5, 1948, Serial No. 58,519

' (o1. 21o-16s) 5 Claims.

This invention relates to filter -units of the kind utilizing areplaceable filter element for removing sediment and other foreignmaterial from a uid flowing under pressure.

The invention has particular, although not limited, reference to filterunits as used in the fuel supply lines of aircraft engines. A highstandard of performance is required of such devices. This fact, coupledwith the need for quick and effective by-pass of a clogged filter andthe desirability of obtaining lightness of weight predictably consistentperformance and simplicity of assembly and disassembly has made fuellters the subject of intensive design effort looking toward improvementin one or more of the above respects.

It is thought that the present invention achieves the design objectivesmore successfully and completely than was heretofore done. Therealization of such purpose is, accordingly, the object of theinvention.

In regard to theby-pass function it is contemplated by this invention tointerpose a pressure relief Valve in parallel with the filter in suchwise that the valve will open under the application of a predeterminedhigh pressure differential to the opposite sides thereof` and .permitthe continuance of fluid flow in the system even though the filter hasbecome clogged. In connection with the valve there is provided a novelseating arrangement therefor, obviating difficulties previouslyencountered resulting from frictonal opposition to motion of the valve.The by-pass mechanism further comprises a, screen in series with thevalve and acting to remove a part of the foreign material in theby-passed fluid, a feature of the invention residing in a yieldingmounting for the screen permitting a pressure relief motion thereof outof the path of fluid flow when the -screen in turn becomes clogged.

A consistent performance of the by-pass means and simplicity of assemblyof the unit is brought about by making the valve and screen and theirassociated parts a sub-assembly which may be installed in and removedfrom the lter housing as a unit, the several elements .of thesubassembly retaining their initial relation irrespective of othervariable factors, such as the height or length of the filter.

In general it has been endeavored, with success, to present a lter unitof improved, simplified construction and operation, particularlyqualified for use in the fuel supply lines of aircraft engines` Otherobjects and other features of the in"en tion will appear from thefollowing description when read in connection with the accompanyingdrawing, wherein:

Fig. 1 is a view of a filter unit in accordance with the instantinvention, the unit being shown in side elevati-on partly broken awayalong a longitudinal plane indicated by the section line I -I of Fig. 2,andv Fig. 2 is a bottom view of the unit of Fg. 1.

Referring to the drawings, a lter unit comprises, in accordance with thepresent inventon, a two part housing structure I!) made up of a pair ofcup shaped elements II and I2 inversely disposed with respect to eachother and with their edges in contacting relation. The contacting edgeshave an overlapping connection afforded by offset flanges thereon toconfine therebetween a ring seal I'3. Within the housing I0 andextending longitudinally between the elements II and I2 is a tie shaftI4. One end of the shaft I 4 is anchored in the bottom of element I2 bya screw threaded reception in a tarped opening I5 therein. The oppositeend of the tie shaft projects into an opening I6 in the dome of elementI I and has a screw threaded reception in the shank of a nut I1. thehead of which overlies the outer surface of housing element II. Theshank of the nut I1 extends into the opening I6 in surrounding relationto the shaft I4 and is in turn surround-ed by a. ring seal I8 held in acounterbore in opening IE by the head of the nut I Housing element I2 isformed with a bo-s I9 dei-lining an opening 2| communicating with theinterior of housing I0. There may be secured to the boss I9, as shown, aconnector 22 for the attachment of a fluid conducting pipe or hose. lineor the like, it being understood that the filter unit is designed foruse in a system flowing fluid under pressure, for example the fuelsupply line of an aircraft engine. Als-o communicating with the interiorof the housing I0 is an orening 23 (Fig. 2) forming part of a fitting24, adapted for connection in the uid flowing system. The boss I9defining opening 2I extends laterally from the si-deof housing elementI2 while opening 23 and tting 24 are at the bottom of element I2, theopening 23 being located in a position offset from the center line ofthe housing. In the installation of the filter unit, opening 2I isconnected to the source of fuel supply and hence serves as the inlet ofthe unit, opening 23 serving as the outlet. In the dome of element II isa drain opening 20. v

The tie shaft I 4 lies approximately in the longitudinal axis of thehousing I0. Within the housing, in spaced concentric relation to the tieshaft, is a cylindrical iilter 25. The main body 23 of the lter iscomposed, as is customarymf a porous material such as loosely compactedpaper. On the opposite ends of the body are relatively stiff rings 21.One .end of the lter 25 rests upon the bottom of housing element I2,such bottom being formed with a flat seating surface 28. In the surface28 is an annular groove receiving a sealing ring 29. The opposite end ofthe lter 25 is closed by a plate 3| resting thereon. Except for itscontact with the bottom of element I2,V the filter 25 lies in spacedrelation to the inner walls of housing I and defines therewith a chamber32 surrounding the filter. The chamber 32 is in Y open continuouscommunication with lthe Yinlet 2| and is supplied with fluid therefrom.In conjunction with the bottom of element I2 and plate 3 I, the filter25 further defines an internal chamber 33 therein. The filter enclosesthat area of the yhousing in which outlet opening'2'3 is located so thatchamber 33 is in continuous .communication with the outlet. Accordingly,the normal path of flow of Vfluid through the unit is'into the chamber32 by way of inlet 2 I, through the porous body 26. of .the filter 215into .the chamber 33 and out of the unit by way of outlet `23.

After a period of use, varying with the condition of the fluid in thesystem, the filter '.25 will become clogged with particles and sedimentremoved from the fluid. The filter is inexpensive and may be replacedbut it is desirable, particularly in Yaircraft fuel line installations,that the flow of fluid be not interrupted until such time as the cloggedfilter may be conveniently removed and replaced. TQ this end means areprovided for directing the fluid from the inlet 2 |v to the outlet 23 inby-paSSng relation to the filter 25.

The plate 3| is formed on its underside and adjacentthe peripherythereof with a stepped down ledge 34 resting on the upper ring 21 of thefilter. Recessed within the ledge 34 is a-ring seal 35 which, inconjunction with the ring seal 29 inhibits the ow of fluid around thefilter into the chamber 33. I nwardly of the ledge .34, onY theunderside of plate 3|., is anannular flat surface 36 while inwardly ofthe surface 35 is an annular groove 31. The area surrounded by groove 31is recessed and the surface 36 outside the groove is stepped down to anextent approximately equal to the depth of the recess. Further, thecentral recessed portion and the surface 36 are radially spaced from thegroove 31, Accordingly there is defined along the edges of the groove 31projecting concentric rings 38 and 39. Opening into the groove 31 andextending longitudinally through the plate 3| is a series of ports 4|spaced in circular fashion about the axis of the plate.

Centrally of the ports 4| is an opening, 4'2 in the plate 3| providedfor the passage of the tie shaft I4 therethrough. The shaft |4 hasmounted thereon a sleeve 43 having a close, substantially uid tight litin the opening 42. The sleeve 43 extends from a point adjacent thebottom of housing element l2 to a point just above the plate 3|'whereits upper or outer end is turned over upon the plate. A nut 44 is inthreaded engagement with the outer end of the tie shaft I4, and, whenturned down upon the end of sleeve 43, effectively locks the plate 3| inplace upon the filter 25. A washer 45 between the nut 44 and sleeve 43prevents fluid ow along the tie shaft I4 within the sleeve 43.

`Surmounting the sleeve 43 within the chamber 33 and beneath the plate3| is a valve 46 comprising a shank portion 41 having a sliding bearingon the sleeve 43 and a disc portion 48 underlying the concentric rings38 and 39. The disc portion 48 of the valve is encased in a rubber orrubberlike sheath 49 providing a soft deformable surface insuring afluid tight contact -of the valve with the seat defined by rings l38 and39. The valve 45 is urged to such seat by a coil spring 5| surroundingthe shank 41 and based upon a retainer 52 which in turn limits upon aspring clip 53 set in the periphery of the sleeve 43. Thus, `the valve46 normally acts, under the urging of spring 5|, to c-lose the ports 4|and deny communication vbetween the chambers 32 and 33 therethrough. Thespring 5| will yield, however under the influence of a predeterminedhigh pressure differential between the chambers 32 and 33, as may resultfrom clogging of the filter 25. Accordingly, whenY that pressureVVdifferential is reached, valve 416 moves away from its seat on plate3|, opening ports 4| for direct lflow from chamber 32 to chamber 33. l

In surrounding relation to the `tie shaft I4 and valve 46 is a screen 54provided in order that there may be removed `from the fluid ley-passedthrough .ports 4| some portion of the foreign material carried thereby.The vscreen 54 is sacklike in shape with the open or outer end thereoffacing the plate 3|. A reinforcement member 55 on the open end is turnedinward and arranged to seat upon the annular flat surface 3,5 of plate3|. `The bottom or closed end of the screen is also provided with areinforcement member 56, the bottom being inverted from such member andattached to a bushing 51. The bushing 51is slidably mounted on the.sleeve 43and rests upon a coil spring 58 interposed between vthebushing and a retainer 59 limiting against a spring clip 5| set in thesleeve 43 adjacent the bottom thereof. The screen 54 has a substantiallyrigid shape, by reason of the reinforcement members and 55, and is urgedbythe. spring 58,upward,or outward into contact with the plate 3|. Allthe fluid entering chamber 33 by way of ports 4| is, there'- fore,normally compelled to pass throughcthe screen 54. Y

The screen 54 may/like thefilter 25, become clogged in use. When .thisoccurs, the pressure differential between the inlet and outlet of theunit again will rise. Applied across the screen 54, a predetermined highpressure differential is effective to compress spring 53, allowing thescreen to move downward or inward away from plate 3|.l The fluid maythen flow around the upper end of the screen directly from the ports 4|to chamber 33 and the outlet.

Thus, in the operation of the unit, flow normally takes place into thechamber 32 by way of inlet 2| and through filter 25 to chamber 33 andthe outlet 2 3. Valve 4 6V is closed at this time and no flow occursthrough the ports 4|. In the event of clogging of the filter 25,however, the ensuing increase in pressure drop between the inlet andoutlet of the lunit is effective to force valve 45 open against theresistance of spring 5| The fluid admitted to chamber 32 then may reachthe outlet by passage in by-passing relation to the filter through theports 4|, the now being strained bythe screen 54 through which it iscaused to pass. In the course of such bypassing iiow, if the screen 54in turn vbecomes clogged, Spring 58 yields to the rising pressuredifferential and allows the screen to move away yfrom its seat on plate3l opening a path of direct ow between the inlet and outlet.

It will be apparent that the invention presents numerous features ofadvantage as compared to fuel filters of the prior art. Among these isthe use of the spaced concentric rings 38 andv 39 to define the seat forvalve 46. Provision of the inner ring 39 obviates the need for a ringseal or other packing between the valve and its supporting post. Thefactor of friction in motion of the valve, which makes the openingpressure of the valve unpredictable and the closing pressure higher thanthe opening pressure, thus is eliminated.

Another feature has to do with the mounting of all moving parts of theunit on the sleeve 43 instead of directly upon the tie shaft I4. Thisadds to the convenience of initial assembly since the plate SI, sleeve43, valve EES and associated parts, and screen 54 and associated partsmay be brought together as a sub-assembly for mounting on the tie shaftI4 as a unit. Further, use of the sleeve 43 permits the sub-assembly ofwhich it is a part to be stationed anywhere along the length of the tieshaft I4 according to the height of the lter element. The openingpressures of the valve 46 and screen 5ft thus are independent of theheight of the filter element which would determine the initialcompression of the springs 5I and 58 were the valve and screen mounteddirectly upon the tie shaft I4.

It is to be understood, however, that insofar as broad functionalfeatures of the invention are concernedy the valve and screen may beconsidered as being mounted directly upon the tie shaft.

Still another feature resides in the mounting of the screen 54 so thatit will relieve itself under a predetermined pressure differential.Advantages of space, weight and cost are gained over more obviousby-pass devices such as a xed screen and separate relief valve.

What is claimed is:

l. A fuel filter unit for use in systems flowing fluid under pressure,comprising a two part housing made up of a pair of cup shaped elementsarranged with their edges in abutting relationship, a tie shaftextending internally between said eleznents and anchored in the bottomsthereof, a cylindrical lter seating in the bottom of one of saidelements and dening externally thereof a chamber in said housing, aplate closing the opposite end of said filter and defining inconjunction therewith a chamber internally of said filter, inlet andoutlet openings in said housing communicating respectively with saidexternal and internal chambers, a circular series of openings in saidplate for the passage of uid from said inlet to said outlet inby-passing relation to said lter, concentric projections on theunderside of said plate dening a valve seat, a disc-like valve slidablymounted on said tie shaft and engageable with said Valve seat to closesaid openings, a sack-shaped screen arranged in surrounding relation tosaid shaft and said valve, a sleeve set in the closed end of said screenand slidably mounted on said tie shaft, the opposite or open end of saidscreen having a seat on the underside of said plate in outwardly spacedrelation to the series of openings therein, and spring mountings forsaid valve and for said screen on said shaft, permitting motion thereofaway from said plate in response to a predetermined rise in the pressuredrop between said inlet and said outlet.

2. A filter unit according to claim 1, characterized by a sleevesurrounding said tie shaft and formed with a flange overlying the outersurface of said plate, the reactant force of said spring mounting beingexerted upon said bushing in a manner to press said plate upon saidlter.

3. A lter unit for use in systems flowing uid under pressure, comprisinga two part housing made up of a pair of cup-shaped elements inverselyarranged with their edges in abutting relationship. a tie shaftextending internally between said elements and anchored in the bottomsthereof, a cylindrical lter seating in the bottom of one of saidelements and defining externally thereof a chamber in said housing, aplate closing the opposite end of said filter and defining inconjunction therewith a chamber internally of said filter, inlet andoutlet openings in said housing communicating respectively with saidexternal and internal chambers, a circular series of openings in saidplate for the passage of fluid from said inlet to said outlet inbypassing relation to said filter, spaced concentric rings on theunderside of said plate defining a valve seat, a disc-like valveunderlying said concentric rings and arranged to seat thereon, asack-shaped screen in surrounding relation to said valve, the open endof said screen engaging the underside of said plate outward of saidconcentric rings, a sleeve slidably mounted on said tie shaft and fixedrelatively to said plate, said valve and the closed end of said screenbeing slidably mounted on said sleeve, and individual resilientconnections between said sleeve and said valve and between said sleeveand said screen urging said valve and said screen toward contact withsaid plate, said connections yielding successively to a predeterminedhigh pressure differential between said inlet and said outlet as may becaused by clogging of said lter and by clogging of said screen.

4. A filter unit for use in systems flowing fluid under pressure,comprising a housing, a shaft rigidly mounted in said housing betweenopposing walls thereof, a cylindrical filter in said housing seated onone of said walls in surrounding relation to said shaft, a plate closingthe open end of said filter and having a central opening therein throughwhich said shaft is passed, a sleeve surmounting said shaft andextending through the central opening in said plate, a fiange on theouter end of said sleeve turned over upon said plate, a lock-nut on saidshaft screwed down upon said ange to x said sleeve relatively to saidplate, a circular series of ports in said plate, a disc-like valveslidably mounted on said sleeve and engageable with the underside ofsaid plate to close said ports, a screen slidably mounted on said sleevebeneath said valve and engageable with the underside of said plateoutwardly of said series of ports, individual springs urging said valveand said screen to seats on the underside of said plate and yieldingunder predetermined pressure differentials applied thereacross, an inletfor the fluid under pressure opening into said housing externally ofsaid filter, and an outlet communicating with the space enclosed by saidfilter.

5. A lter unit according to claim 4, characterized by individualmounting means for said valve and screen springs on said sleeve, theassembly of parts comprising said sleeve, said 7 plate, said valve, said'screen and said springs Y UNITED STATES PATENTS comprising a. unitarysub-assembly constructed Number Name Date and arranged to be mountedupon said shaft in 511 798 Rankme Y Y Jan 2 1894 cooperative relationwith the filter Without 2 017350 Morgan Y Oct15 1935 alteration in theinitial tension of the springs 5 2389814 Pond et 3"? "Nov 27 1945irrespective of the height or length of the filter. F* V Y j MILES H.1A1vI11;.'I0i-Ii OREIGN PATENTS Numberv Country p Date REFERENCES CITED520.779 Great Britain m- May 3, 1940 Th following references are ofrecord in the 10 l of this patent:

